In a device disclosed in Patent Document 1, a camshaft penetrates through an elongated hole formed in a movable cam. This allows the movable cam to eccentrically rotate in relation to the camshaft, and to reciprocate in a radial direction by a reactive force received from a valve in response to the rotation of the camshaft. A plunger that is biased by a spring and extends by the effect of hydraulic pressure is located between the camshaft and the movable cam. When the hydraulic pressure is not exerted, the plunger extends and contracts, and the movable cam is allowed to reciprocate in the radial direction with respect to the camshaft. When the hydraulic pressure is exerted, the plunger is maintained at the extended state, and the position of the movable cam relative to the camshaft is fixed.